Additive composition for a metal working fluid

ABSTRACT

An additive composition for a metalworking fluid which comprises a reaction product obtainable by the reaction between a molar excess of an anhydride and an amine, wherein the amine is at least one amino alkyl mono- or di- alkanolamine, in particular having a structural formula (I): HOOC—R—CO—NH—X—N(R′)—Y—O—CO—R′′—COOH, wherein: X represents an alkyl group having 1 to 12 carbon atoms, preferably, 2 to 8 carbon atoms and more preferably 3 to 6 carbon atoms; Y represents a hydrocarbyl group having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms; R′ represents an alkyl or alkanol groups having 2 to 12 carbon atoms; and R and R″ independently represent hydrocarbyl groups which have up to 48 carbon atoms, preferably 2 to 28; more preferably 6 to 13 carbon atoms.

[0001] The present invention relates to an additive composition for a metalworking fluid.

[0002] Aqueous fluids are used extensively as metalworking fluids due to their lubricity and cooling capacity. Synthetic, or completely water-based fluids, have additional advantages of low misting, improved cleanliness and safety. However, most of these fluids are not waste-treatable using simple conventional methods. In large part, this is due to their lubricity and corrosion inhibiting additives. Suitable organic inhibitors include phosphate esters, fatty acids, amines and aromatic acids. Such compounds, however, tend to have high chemical oxygen demand levels (COD). As a result, it can be difficult to reduce the COD of fluids containing such inhibitors to acceptable levels, particularly when simple waste treatment techniques are employed. Although inorganic corrosion inhibitors, such as clay and metal borates, do not affect the COD levels of metalworking fluids, such inhibitors tend to form hard residues, especially when the water used to dilute the metalworking fluid contains high levels of naturally occurring elements such as calcium or magnesium. These hard residues have negative effects, particularly on the machine or parts.

[0003] It is among the objects of the present invention to provide an alternative composition for a metal-working fluid.

[0004] According to the present invention, there is provided an additive composition for a metalworking fluid, said additive composition comprising a reaction product obtainable by the reaction between a molar excess of an anhydride and an amine, wherein the amine is at least one amino alkyl mono- or di-alkanolamine.

[0005] Where a mixture of two different alkanolamines is employed, the mixture preferably comprises a primary alkanolamine and a secondary alkanolamine, and/or a primary alkanolamine and a tertiary alkanolamine.

[0006] Any suitable anhydride may be used to produce the additive composition of the present invention. Preferably, a polycarboxylic acid anhydride is employed. More preferably, the polycarboxylic acid anhydride is a dicarboxylic acid anhydride. Suitable dicarboxylic acid anhydrides include succinic, phthalic, glutaric, pimelic, suberic, azelaic and sebacic anhydrides. Such anhydrides may comprise up to 50 carbon atoms, for example, 4 to 30, preferably, 8 to 15 carbon atoms. Additionally, these anhydrides may further comprise aliphatic hydrocarbyl substituents, for example, saturated or unsaturated hydrocarbyl substituents. These substituents include C₁ to C₂₅, preferably, C₄ to C₁₈, more preferably, C₆ to C₁₂ alkyl and/or alkenyl groups, for example, a C₈ alkyl or alkenyl group. In preferred embodiments, succinic and phthalic anhydrides are employed. In a most preferred embodiment, the anhydride is octenyl succinic anhydride.

[0007] Where an amino alkyl di-alkanolamine is employed, the amino alkyl di-alkanolamine preferably has an alkyl group of 1 to 12 carbon atoms, more preferably, 2 to 8 carbon atoms, and most preferably, 3 to 6 carbon atoms. For example, the alkyl group may be an ethyl, propyl, butyl, pentyl or hexyl group. The amino alkyl di-alkanolamine may have a di-alkanolamine group having 2 to 12 carbon atoms, preferably, 2 to 6 carbon atoms. For example, the di-alkanolamine may be derived from an unsubstituted and/or substituted diethanolaamine, dipropanolamine, di-t-butanolamine, diisopropanolamine, 2,2′-iminbutanol, 3,3′-iminodipentanol-2, and/or N-(hydroxyethyl)-propanolamine. For the avoidance of doubt, an amino alkyl di-alkanolamine is a secondary dialkanolamine: in this application, the terms have been used interchangeably.

[0008] Where a mixture of a primary alkanolamine and a secondary alkanolamine or tertiary alkanolamine is employed, the primary alkanolamine preferably has an alkyl group of 1 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and most preferably 3 to 6 carbon atoms. For example, the primary amine may be derived from an unsubstituted and/or substituted monoethanolamine, monoisopropanolamine, diglycolamine and/or 2-amino-2-methyl-1-propanol. The secondary or tertiary amine preferably has an alkyl group of 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 4 to 8 carbon atoms. Suitable secondary amines are described above in the preceding paragraph. A preferred secondary amine is one derived from a di-isopropanolamine. Suitable tertiary amines include those derived from, 2-dimethylamino-2-methyl-1-propanol, and/or bis-hydroxylethylmethylamine.

[0009] In a preferred embodiment, the amine is amino propyl di-iso-propanolamine (APDIPA).

[0010] In a most preferred embodiment, the reaction product is a reaction product of aminopropyl di-iso-propanolamine (CAS#77355-06-7) and octenyl succinic anhydride.

[0011] The mole ratio of amine to anhydride employed may be in the range of 0.1 to less than 1:1, preferably, 0.2 to less than 1:1, more preferably, 0.4 to less than 1:1, for example, 0.6:1. In a most preferred embodiment, the reaction product is a reaction product of amino propyl di-iso-propanolamine and octenyl succinic anhydride, wherein the mole ratio of amine to anhydride employed is 0.5:1.

[0012] The reaction product may be produced by reacting the anhydride and the amine at a reaction temperature of 80 to 200° C., preferably, 100 to 180° C., more preferably, 130 to 160° C.

[0013] According to a further embodiment of the present invention there is provided a compound having a structural formula (I):

HOOC—R—CO—NH—X—N(R′)—Y—O—CO—R″—COOH   (I).

[0014] wherein:

[0015] X represents an alkyl group having 1 to 12 carbon atoms, preferably, 2 to 8 carbon atoms and more preferably 3 to 6 carbon atoms;

[0016] Y represents a hydrocarbyl group having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms;

[0017] R′ represents an alkyl or alkanol group having 2 to 12 carbon atoms; and

[0018] R and R″ independently represent hydrocarbyl groups which have up to 48 carbon atoms, preferably 2 to 28, more preferably 6 to 13 carbon atoms.

[0019] R and R′ may independently comprise aliphatic hydrocarbyl substituents, preferably C₁ to C₂₅, preferably, C₄ to C₁₈, more preferably, C₆ to C₁₂ alkyl and/or alkenyl groups, for example, a C₈ alkyl or alkenyl group.

[0020] A preferred compound according to formula I is butanedioic acid, octenyl-, mono(2-((3-((3-carboxyoctenyl-1-oxopropyl)amino)propyl)(2-hydroxypropyl)amino-1-methylethyl) ester CAS number: 384370-64-3 and represented by the formula II

[0021] In addition to the reaction product, the additive composition may also comprise water and other conventional additives for metal-working fluids. Suitable additives include lubricity additives, such as polyalkylene oxides, phosphate esters, fatty acids, fatty acid esters and derivatives thereof. Suitable polyalkylene oxides and polyoxyalkylene derivatives include polyoxyethylene, polyoxypropylene, oxyethylene oxypropylene (block) polymer, ethylene oxide propylene oxide (block) additive of ethylenediamine. Suitable phosphate ester derivatives include polyoxyethylene octadecenyl ether phosphates, polyoxyethylene hexyl ether phosphates and polyoxyethylene laural ether phosphates. Suitable fatty acids include fatty acids of 4 to 40 carbon atoms, preferably, 6 to 24 carbon atoms, more preferably, 8 to 20 carbon atoms. Specific examples of suitable fatty acids include stearic acid, palmitic acid, myristic acid, lauric acid, arachic acid, behenic acid, myristoleic acid, palmitoleic acid, oleic acid, linolic acid, linoleic acid, eleostearic acid, hydroxystearic acid and ricinolic acid. Salts, for example, metal salts of such acids may be employed. Alkali metal salts are preferred; examples include potassium and sodium salts. Suitable fatty acid esters include fatty acid polyglycol esters, such as 9-octadecanoic acid (Z)-, 1-methylethyl ester. De-foamers, biocides and/or additional corrosion inhibitors, such as benzotriazole may also be present in the additive composition.

[0022] The additive composition of the present invention may be added to a metalworking fluid, for example, as a corrosion inhibitor. Thus, according to a further aspect of the present invention, there is provided a metalworking fluid composition comprising a metalworking fluid and the reaction product of the additive composition described above. The metalworking fluid typically comprises greater than 50 wt % water, preferably, greater than 70 wt % water, preferably, between 70 and 99 wt % water. Examples of suitable metal-working fluids include those from the Castrol Syntilo® range, such as Castrol Syntilo® 9902, Castrol Syntilo® 9904, Castrol Syntilo® 9913, Castrol Syntilo® 9930, Castrol Syntilo® 9951, Castrol Syntilo® 9954 and Castrol Syntilo® E-55.

[0023] Preferably, the reaction product forms 1 to 50 wt %, more preferably, 10 to 30 wt %, most preferably, 15 to 20 wt % of the overall metalworking fluid composition.

[0024] The metal-working fluid composition may further comprise lubricity additives, such as polyalkylene oxides, phosphate esters, fatty acids, fatty acid esters and derivatives thereof. Suitable polyalkylene oxides and polyoxyalkylene derivatives include polyoxyethylene, polyoxypropylene, oxyethylene oxypropylene (block) polymer, ethylene oxide propylene oxide (block) additive of ethylenediamine. Suitable phosphate ester derivatives include polyoxyethylene octadecenyl ether phosphates, polyoxyethylene hexyl ether phosphates and polyoxyethylene laural ether phosphates. Suitable fatty acids include fatty acids of 4 to 40 carbon atoms, preferably, 6 to 24 carbon atoms, more preferably, 8 to 20 carbon atoms. Specific examples of suitable fatty acids include stearic acid, palmitic acid, myristic acid, lauric acid, arachic acid, behenic acid, myristoleic acid, palmitoleic acid, oleic acid, linolic acid, linoleic acid, eleostearic acid, hydroxystearic acid and ricinolic acid. Salts, for example, metal salts of such acids may be employed. Alkali metal salts are preferred; examples include potassium and sodium salts. Suitable fatty acid esters include fatty acid polyglycol esters, such as 9-octadecanoic acid (Z)-, 1-methylethyl ester. De-foamers, biocides and/or additional corrosion inhibitors, such as benzotriazole may also be present in the metalworking fluid composition.

[0025] According to a preferred embodiment, the metalworking fluid composition comprises independently by weight: Water 40-90% e.g. 45-90% Reaction Product  2-50% e.g. 5-40% C6-C12 Fatty acids/potassium salts  5-15% e.g. 5-10% Benzotriazole  0-5% e.g. 0-1% Defoamer  0-1% Biocides  0-1%

[0026] The metalworking fluid composition of the present invention may be employed in any metal-working application, for example, in cutting and/or grinding. The metal-working fluid composition may be used to work a range of metals, including for example, iron, steel and aluminium.

[0027] An advantage of the metal-working fluid composition of the present invention is that it is waste-treatable, particularly, using conventional waste-treatment methods. Thus, the COD level of the composition may be reduced to acceptable values of 10,000 mg/l or less, preferably, to 2000 mg/l or less, more preferably, to 1500 mg/l or less using conventional waste-treatment techniques. The COD may not be reduced to zero and may be at least 200, 500 or 600 mg/l. Preferably, such conventional waste-treatment techniques may be used to reduce the initial COD levels of the metal-working fluid composition by more than 20%, preferably, more than 50%.

[0028] Conventional waste-treatment methods for metalworking fluids are described in detail in “Waste Minimization and Wastewater Treatment of Metalworking Fluids” by Jean C Childers, Shu-Jen Huang and Michael Romba; @1990 Independent Lubricant Manufactures Association. Such methods include evaporation, ultra-filtration and chemical treatment using, for example, polymer or acid/alum methods. Of these methods, acid/alum splits are particularly useful for reducing the COD of the metalworking fluid compositions of the present invention to acceptable levels. This form of chemical treatment is based on the principle of neutralization of surface charges. Typically, the pH of the solution to be waste treated is lowered with a strong acid (sulfuric acid) to a pH of 2.5. At this point, aluminum sulfate is added to the solution. Then, slowly raising the pH with the addition of sodium hydroxide will facilitate the formation of aluminum hydroxide which will attract the anionic particles and form an insoluble floc, causing separation from the aqueous phase.

[0029] Yet another aspect of the present invention provides the use of the additive composition described above, as a corrosion inhibitor for a metal-working fluid.

[0030] These and other aspects of the invention will now be described, by way of illustration, with reference to the following examples.

EXAMPLE 1

[0031] APDIPA and octenyl succinic anhydride were reacted together at a molar ratio of 0.5:1 to form a mixture of anhydride and amide, at approximately 150° C. for 4 hours. The reaction product was isolated for further use.

EXAMPLE 2

[0032] In this Example, the solution produced in Example 1 was incorporated into an experimental metalworking fluid formulation to test its corrosion inhibiting properties. More specifically, 4 grams of cast iron chips were placed in a petri dish and partially covered with 6 mls of diluted product (product diluted to 5% in 600 ppm CaCl₂ water). The cast iron chips and diluted fluid are then transferred to a petri dish containing filter paper and covered for 2 hours. After 2 hours, the cast iron chips are uncovered and exposed to air for 24 hours. After this time, approximately 10% of the filter paper showed signs of corrosion.

Comparative Example A

[0033] In this Example, Example 2 was repeated using a product consisting of a blend of APDIPA and Bis-hydroxylethylmethylamine reacted with Octenyl Succinic Anhydride at a 0.7:1.0 molar ratio. In this example, 40% of the filter paper showed signs of corrosion.

EXAMPLE 3

[0034] The COD level of the solution of Example 2 was tested using EPA Method 410.1. The COD level of the solution was found to be 4800 mg/l.

Comparative Example B

[0035] Example 3 was repeated using a solution of APDIPA reacted-with Phthalic Anhydride at a 1:1 molar ratio. The COD level of this solution was found to be 4400 mg/l.

EXAMPLE 4

[0036] The solution of Example 2 was treated using a conventional acid/alum split. The COD of the treated solution was found to have reduced to 800 mg/l.

Comparative Example C

[0037] Example 4 was repeated using the solution of Comparative Example B. The COD level of this solution was found to be 4000 mg/l.

Comparative Example D

[0038] Example 4 was repeated using the solution of Comparative Example A. The COD level of this solution was found to be 1000 mg/l.

Comparative Example E

[0039] Example 4 was repeated using a solution of Aminopropyl Diethanolamine ( APDEA) reacted with Tetrapropenyl Succinic Anhydride (TPSA) at a 1:1 molar ratio. The COD level of this solution was found to be 1600 mg/l.

Comparative Example F

[0040] Example 4 was repeated using a solution of APDIPA reacted with Methyl Nadic Anhydride at a 1:1 molar ratio. The COD level of this solution was found to be 4800 mg/l.

Comparative Example G

[0041] Example 4 was repeated using a solution of APDIPA reacted with Dodecyl Succinic Anhydride at a 1:1 molar ratio. The COD level of this solution was found to be 1800 mg/l. 

We claim:
 1. An additive composition for a metalworking fluid, said additive composition comprising a reaction product obtainable by the reaction between a molar excess of an anhydride and an amine, wherein the amine is at least one amino alkyl mono- or di-alkanolamine.
 2. An additive composition as claimed in claim 1 in which said anhydride comprises up to 50 carbon atoms, preferably 4 to 30 carbon atoms, more preferably 8 to 15 carbon atoms.
 3. An additive composition as claimed in claim 1 or claim 2 in which said anhydride is a polycarboxylic acid anhydride.
 4. An additive composition as claimed in claim 3 in which said anhydride is a dicarboxylic acid anhydride.
 5. An additive composition as claimed in claim 4 in which said anhydride is selected from the group consisting of succinic, phthalic, glutaric, pimelic, suberic, azelaic and sebacic anhydrides.
 6. An additive composition as claimed in any preceding claim in which said anhydrides further comprise aliphatic hydrocarbyl substituents.
 7. An additive composition as claimed in claim 6 in which said substituents include C₁ to C₂₅, preferably, C₄ to C₁₈, more preferably, C₆ to C₁₂ alkyl and/or alkenyl groups, for example, a C₈ alkyl or alkenyl group.
 8. An additive composition as claimed in claim 1 in which said anhydride is octenyl succinic anhydride.
 9. An additive composition as claimed in any preceding claim in which said amino alkyl di-alkanolamine preferably has an alkyl group of 1 to 12 carbon atoms, more preferably, 2 to 8 carbon atoms, and most preferably, 3 to 6 carbon atoms.
 10. An additive composition as claimed in any preceding claim in which the alkyl group of said amino alkyl dialkanolamine is selected from the group consisting of ethyl, propyl, butyl, pentyl and hexyl groups.
 11. An additive composition as claimed in any one of the preceding claims in which the amino alkyl di-alkanolamine has a di-alkanolamine group having 2 to 12 carbon atoms, preferably, 2 to 6 carbon atoms.
 12. An additive composition as claimed in claim 11 in which the di-alkanolamine is derived from an unsubstituted and/or substituted diethanolamine, dipropanolamine, di-t-butanolamine, diisopropanolamine, 2,2′-iminbutanol, 3,3′-iminodipentanol-2, and/or N-(hydroxyethyl)-propanol amine.
 13. An additive composition as claimed in claim 11 in which the di-alkylalkanolamine is aminopropyl di-iso-propanolamine (APDIPA).
 14. An additive composition as claimed in claim 13 which comprises the reaction product of amino propyl di-iso-propanolamine and octenyl succinic anhydride, preferably in a mole ratio of amine to anhydride of 0.5:1.
 15. A compound having a structural formula (I): HOOC—R—CO—NH—X—N(R′)—Y—O—CO—R″—COOH   (I). wherein: X represents an alkyl group having 1 to 12 carbon atoms, preferably, 2 to 8 carbon atoms and more preferably 3 to 6 carbon atoms; Y represents a hydrocarbyl group having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms; R′ represents an alkyl or alkanol group having 2 to 12 carbon atoms; and R and R″ independently represent hydrocarbyl groups which have up to 48 carbon atoms, preferably 2 to 28, more preferably 6 to 13 carbon atoms.
 16. A compound as claimed in claim 15 in which R and R″ independently comprise aliphatic hydrocarbyl substituents, preferably C₁ to C₂₅, preferably, C₄ to C₁₈, more preferably, C₆ to C₁₂ alkyl and/or alkenyl groups, for example, a C₈ alkyl or alkenyl group.
 17. A compound as claimed in claim 15 in which R and R″ together with their associated COOH and CO groups are octenyl substituted succinate groups, X is an n-propyl group, Y is an isopropyl group and R′ is an isopropanol group.
 18. A process for preparing an additive composition as claimed in any one of claims 1 to 14 or for preparing a compound as claimed in any one of claims 15 to 17 which comprises reacting a molar excess of an anhydride and an amine, wherein the amine is at least one amino alkyl mono- or di- alkanolamine.
 19. A process as claimed in claim 18 in which the mole ratio of amine to anhydride is in the range 0.1 to less than 1:1, preferably 0.2 to less than 1:1, more preferably 0.4 to less than 1:1 and most preferably 0.5:1.
 20. A process as claimed in claim 18 or 19 in which the reaction is performed at a temperature of 80 to 200° C., preferably, 100 to 180° C., more preferably, 130 to 160° C.
 21. An additive composition as claimed in any one of claims 1 to 14 which further comprises water and at least one lubricity additive selected from the group consisting of polyalkylene oxides, phosphate esters, fatty acids, fatty acid esters and derivatives thereof.
 22. A metalworking fluid comprising an additive composition as claimed in any one of claims 1 to 14 or 21, or as prepared by a process as claimed in any one of claims 18 to 20 or comprising a compound as claimed in any one of claims 15 to
 17. 23. A metalworking fluid as claimed in claim 22 comprising 1 to 50 wt % of a reaction product of a process as claimed in any one of claims 18 to
 20. 24. A metalworking fluid as claimed in claim 22 or claim 23 further comprising at least one lubricity additive selected from the group consisting of polyalkylene oxides, phosphate esters, fatty acids, fatty acid esters and derivatives thereof.
 25. A metalworking fluid as claimed in claim 24 which comprises by weight: water, 40-90%; Reaction Product, 2-50%; C₆-C₁₂ Fatty acids/potassium salts, 5-15%; benzotriazole, 0-5%; defoamer, 0-1% and biocides, 0-1%.
 26. A method of metalworking which comprises employing a metalworking fluid as claimed in any one of claims 22 to
 25. 27. Use of an additive composition as claimed in any one of claims 1 to 14 or 21, or as prepared by a process as claimed in any one of claims 18 to 20 or comprising a compound as claimed in any one of claims 15 or 17 as a corrosion inhibitor for a metalworking fluid. 